Solvent fractionation of hydrocarbon oils



Patented Sept. 7, 1937 N Ti? TED SOLVENT FRACTIONATION F HYDROCAB- BONOILS Maurice H. Arveson, Hammond, Ind, assignor to Standard Oil Company,Chicago, 111., a corporation of Indiana No Drawing.

Application June 28, 1934,

Serial No. 732,834

13 Claims. (Cl. 196-43) My invention relates to the solventfractionation of hydrocarbon oils, particularly to the solventextraction of naphthas and still more particularly to the solventfractionation of cracked naphthas, by means of certain new and superiorceeds.

Phenol and other phenolic substances have been used or proposed for thesolvent fractionation of lubritrting oil stocks. These substances arenot generally suitable to the solvent fractionation of lighterhydrocarbon oils such as naphthas and particularly cracked naphthas forreasons which will "be brought out below. I have found that certain newcombinations of solvents comprising at least one phenolic substancetogether with liquid ammonia are highly superior for thesolventfractionation of these light hydro carbon oils.

The solvent fractionation of naphthas is important as a method ofobtaining a fraction of high antiknock value, or in other words of highoctane number, for use as a motor fuel or motor fuel component.

It is desirable that a solvent fractionation process should, ifpossible, be operated at ordinary atmospheric temperatures or ,attemperatures somewhat above atmospheric rather thanat low temperaturessince in the latter case expensive refrigeration is required. Forlthisreason, the use of a phenolic substance, for instance cresylic acid, inthe solvent fractionation ofnaphthas is not satisfactory since themiscibility temperature, i. e. the temperature at which two liquidphases commence to form, is generally such as to require considerablerefrigeration. Thus, for instance, When 62% by volume of cracked heavypetroleum naphtha was dissolved in 38% of cresylic acid the solution wasstill clear when the temperature was lowered to 0 F.- This indicatesthat a considerably lower temperature would be necessary in order toseparate two liquid phases if any separation takes place at all. Incontrast with this result, it was found that when 49% by volume of thissame naphtha was mixed with 30% by volume of cresylic acid and 21 byvolume of liquid ammonia the miscibility temperature was about 110 F. orin other words two liquid phases were present at temperatures below 110F. The addition of a larger amount of ammonia makes possible even highermiscibility temperatures. Thus, for instance, when 32% by volume ofcracked heavy petroleum naphtha was dissolved in 19% by volume ofcresylic acid and 49% by volume of liquid ammonia it was found thattwo'layers existed, each in substantial volume,"at 110 F., demonstratingthat the miscibility temperature was considerably above this figure. Asanother example, a sample of cracked heavy petroleum naphtha wasvigorously agitated with one-half its volume of liquid ammonia andone-half its volume of cresylic acid at F. and it was found that twolayers separated readily.

In any of these cases where two liquid layers are formed by the use ofammonia and a phenolic substance, the raflinate layer (usually the upperlayer) contains the low octane number constituents of the originalnaphtha and the extract layer contains the bulk of the phenolicsubstance and.

' the more valuable high octane number constituents of the originalnaphtha. Thus, for example, when one volume of cracked heavy naphthaderived from Mid-Continent crude oil was extracted with one-half volumeof cresylic acid and onehalf volume of liquid ammonia at F., two liquidlayers were formed. These were separated, the solvents were removed fromthe naphtha constituents and it was found that the extract fraction hadan octane number of 94 as compared with an octane number of 62 for theoriginal cracked heavy naphtha stock and an octane number of 48.5 forthe raflinate fraction.

I prefer to conduct the extraction so as to produce an extract productwith a knock rating above '70 octane number. By varying the conditions,degree of extraction, etc., I can produce by my process, gasolineshaving knock ratings up to octane number, depending on the stockemployed and the degree of extraction applied.

Various phenolic compounds can be used together with liquid ammonia inmy process. As examples of these, I may mention phenol itself; theortho, meta and para oresols; the mixed cresol's, known as cresylicacid; the xylenols; 45

prefer, however, to keep the volumetric ratio of solvent to stock withinthe limits of from 1:1 to 5:1. The ratio of liquid ammonia to phenolicsubstance can also be varied within considerable 5 limits depending onthe results desired, the particular stock used, the temperature at whichit is desired to operate, etc. In general, the greater the proportion ofammonia the higher will be the miscibility temperature. I may use fromby volume of liquid ammonia and 90% by volume of phenolic substance to90% by volume of liquid ammonia and 10% by volume of phenolic substance.I prefer, however, to keep within the range of from 25% by volume ofliquid ammonia and 75% by volume of phenolic substance to 25% by volumeof liquid ammonia and 25% by volume of phenolic substance. Thirdcomponents can also be added to the solvent mixture to increaseselectivity or to render the solvent mixture either more or lessmiscible with the hydrocarbon oil. Thus,-for instance, miscibility canbe increased, if desired, by the addition of anhydrous ethanol oracetone.

It will be understood that my new solvent mix- 1 tures can be applied inany of the known types of solvent fractionation process. Thus, forexample, the solvent mixture and stock can be heated above themiscibility temperature to form a homogeneous solution and then cooledto form two separate layers or phases and these can then be separatedfrom each other and the solvent recovered from each of them. On theother hand, my process can be operated by co-agitating the solventmixture and stock at a temperature below the miscibility temperature andthen separating the two liquid phases, removing solvent, etc. Thevarious types of countercurrent processes known to the art or which mayhereafter be devised can also be used. Thus, for instance, the

40 stock can be introduced at the bottom of a countercurrent extractiontower and the solvent mixture can be introduced at the top, the twoliquids flowing countercurrent to each other at tempera- I tures belowthe miscibility temperature, an extract phase being removed at thebottom and a rafiinate phase at the top of the tower. When operated in acountercurrent system the two componentsof the solvent mixture can, ifdesired, be introduced at difierent points in the system. A stagecountercurrent system can likewise. be used.

Various methods can be employed for the removal of the solvents from theextract and raffinate phases. Thus, if the naphtha is sufliciently lighta high boiling phenolic substance such as cresol or xylenol can beseparated by distilling ofi the naphtha and ammonia leaving the phenolicsubstance as a bottom. The ammonia can readily be separated from thenaphtha by fractional distillation due to its low boiling point or 0 bywater washing, or it can be condensed along with the naphtha, in whichcase it will separate as a distinct layer or phase due to its almostcomplete immiscibility with the naphtha. On the other hand, if thenaphtha being extracted is a 5 heavy one. and the phenolic substanceused is phenol, the latter can be distilled off from the naphtha alongwith the ammonia. Another efficient method of removing the phenolicsubstance from the extract and/or rafiinate portion of the '70 naphthais by the use of an excess of ammonia.

The procedure according to this method is, in brief, to contact theextract or rafi'inate phase containing the phenolic substance with alarge excess of liquid ammonia which will dissolve the 75 phenolicsubstance away from the naphtha withaceaiee out dissolving the naphtha.This can most efficiently be done in a tower or by other countercurrentextraction method. Water can be used in small quantities to aid phaseseparation.

The stock on which my process is operated is preferably a hydrocarbonmaterial containing substantial amounts of material within the gasolineboiling point range. It may suitably be a crude gasoline or any type ofnaphtha, usually with a knock rating below 65 octane number. The processis, however, particularly adapted to the fractionation of heavypetroleum naphthas, i. e., materials consisting predominantly ofhydrocarbons boiling between about 250 F. and about 400 F. Still moreparticularly, my process is adapted to fractionation of heavy petroleumnaphthas produced by cracking processes and known as cracked heavynaphthas and still more particularly to cracked heavy petroleum naphthasproduced by vapor phase cracking processes and containing highconcentrations of olefinic hydrocarbons. Thus, for instance, a vaporphase cracked naphtha containing at least-25% of olefinic hydrocarbonsand preferably at least 40% of olefinic hydrocarbons is a highlydesirable charging stock for my process. The raifinate from my processcan be returned to a cracking operation again to produce olefinichydrocarbons and various types of combination processes involvingsolvent fractionation on the one hand and cracking on the other hand canbe used. The term cracking as used herein also covers the so-calledre-forming processes and the term cracked naphtha includes re-formednaphtha.

While I have described my invention in connection with certain specificembodiments and in connection with certain theories of operation, itwill, be understood that these are by way of illustration rather than byway of limitation, and I do not desire to restrict myself thereto exceptto the broadest valid interpretation of the appended claims in which Ihave set forth the novel features of my invention.

I claim:

1. A process for the solvent fractionation of a petroleum oil comprisingcontacting said oil with a substantial amount of at least one phenolicsubstance and a substantial amount of liquid ammoma.

2. A process according to claim 1 in which said at least one phenolicsubstance comprises cresylic acid.

3. A process according to claim 1 in which said oil consistspredominantly of hydrocarbons boiling between about 250 F. and about 400F.

4. A process according to claim 1 in which said oil is a crackedpetroleum naphtha.

5. A process for the solvent fractionation of a cracked petroleumnaphtha consisting predominantly of hydrocarbons boiling between about250 F. and about 400 F., comprising contacting said cracked petroleumnaphtha with a substantial amount of at least one phenolic substance anda. substantial amount of liquid ammonia at a temperature belowthe-miscibility temperature of the system thus formed, whereby raflinateand extract phases are formed, the extract phase containing hydrocarbonshaving an octane number of at least 70, and separating said extract andraifinate phases.

6. A process according to claim 5 in which said at least one phenolicsubstance is cresylic acid.

7. A process for the solvent fractionation of a cracked petroleumnaphtha consisting predominantly of. hydrocarbons boiling between about250 F. and about 400 F., comprising contacting said cracked petroleumnaphtha with from 1 to 5 times its volume of a mixed solvent comprisingfrom 25% to 75% by volume of at least one phenolic substance and from25% to 75% by volume of liquid ammonia at a temperature below themiscibility temperature of the system thus formed, whereby raflinate andextract phases are formed, the extract phase containing hydrocarbonshaving an octane number of at least 70, and separating said extract andraiiinate phases.

8. A process according to claim 7 in which said petroleum naphtha is aproduct of a vapor phase cracking operation.

9. A process according to claim 7 in which said at least one phenolicsubstance is cresylic acid.

10. A process according to claim 7 in which said petroleum naphtha is aproduct of a vapor phase cracking operation and said at least onephenolic substance is cresylic acid.

11. A process for separating oil into fractions comprising extractingsaid oil with phenol or its homologues and ammonia to form a rafiinate-

